LXR linux/net/ipv4/xfrm4_mode

   1/*
   2 * xfrm4_mode_tunnel.c - Tunnel mode encapsulation for IPv4.
   3 *
   4 * Copyright (c) 2004-2006 Herbert Xu <herbert@gondor.apana.org.au>
   5 */
   6
   7#include <linux/init.h>
   8#include <linux/kernel.h>
   9#include <linux/module.h>
  10#include <linux/skbuff.h>
  11#include <linux/stringify.h>
  12#include <net/dst.h>
  13#include <net/inet_ecn.h>
  14#include <net/ip.h>
  15#include <net/xfrm.h>
  16
  17static inline void ipip_ecn_decapsulate(struct sk_buff *skb)
  18{
  19        struct iphdr *inner_iph = ipip_hdr(skb);
  20
  21        if (INET_ECN_is_ce(XFRM_MODE_SKB_CB(skb)->tos))
  22                IP_ECN_set_ce(inner_iph);
  23}
  24
  25/* Add encapsulation header.
  26 *
  27 * The top IP header will be constructed per RFC 2401.
  28 */
  29static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
  30{
  31        struct dst_entry *dst = skb_dst(skb);
  32        struct iphdr *top_iph;
  33        int flags;
  34
  35        skb_set_network_header(skb, -x->props.header_len);
  36        skb->mac_header = skb->network_header +
  37                          offsetof(struct iphdr, protocol);
  38        skb->transport_header = skb->network_header + sizeof(*top_iph);
  39        top_iph = ip_hdr(skb);
  40
  41        top_iph->ihl = 5;
  42        top_iph->version = 4;
  43
  44        top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);
  45
  46        /* DS disclosed */
  47        top_iph->tos = INET_ECN_encapsulate(XFRM_MODE_SKB_CB(skb)->tos,
  48                                            XFRM_MODE_SKB_CB(skb)->tos);
  49
  50        flags = x->props.flags;
  51        if (flags & XFRM_STATE_NOECN)
  52                IP_ECN_clear(top_iph);
  53
  54        top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
  55                0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
  56        ip_select_ident(top_iph, dst->child, NULL);
  57
  58        top_iph->ttl = dst_metric(dst->child, RTAX_HOPLIMIT);
  59
  60        top_iph->saddr = x->props.saddr.a4;
  61        top_iph->daddr = x->id.daddr.a4;
  62
  63        return 0;
  64}
  65
  66static int xfrm4_mode_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
  67{
  68        const unsigned char *old_mac;
  69        int err = -EINVAL;
  70
  71        if (XFRM_MODE_SKB_CB(skb)->protocol != IPPROTO_IPIP)
  72                goto out;
  73
  74        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
  75                goto out;
  76
  77        if (skb_cloned(skb) &&
  78            (err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
  79                goto out;
  80
  81        if (x->props.flags & XFRM_STATE_DECAP_DSCP)
  82                ipv4_copy_dscp(XFRM_MODE_SKB_CB(skb)->tos, ipip_hdr(skb));
  83        if (!(x->props.flags & XFRM_STATE_NOECN))
  84                ipip_ecn_decapsulate(skb);
  85
  86        old_mac = skb_mac_header(skb);
  87        skb_set_mac_header(skb, -skb->mac_len);
  88        memmove(skb_mac_header(skb), old_mac, skb->mac_len);
  89        skb_reset_network_header(skb);
  90        err = 0;
  91
  92out:
  93        return err;
  94}
  95
  96static struct xfrm_mode xfrm4_tunnel_mode = {
  97        .input2 = xfrm4_mode_tunnel_input,
  98        .input = xfrm_prepare_input,
  99        .output2 = xfrm4_mode_tunnel_output,
 100        .output = xfrm4_prepare_output,
 101        .owner = THIS_MODULE,
 102        .encap = XFRM_MODE_TUNNEL,
 103        .flags = XFRM_MODE_FLAG_TUNNEL,
 104};
 105
 106static int __init xfrm4_mode_tunnel_init(void)
 107{
 108        return xfrm_register_mode(&xfrm4_tunnel_mode, AF_INET);
 109}
 110
 111static void __exit xfrm4_mode_tunnel_exit(void)
 112{
 113        int err;
 114
 115        err = xfrm_unregister_mode(&xfrm4_tunnel_mode, AF_INET);
 116        BUG_ON(err);
 117}
 118
 119module_init(xfrm4_mode_tunnel_init);
 120module_exit(xfrm4_mode_tunnel_exit);
 121MODULE_LICENSE("GPL");
 122MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_TUNNEL);
 123